<!--
任务
1. 搭建基础的bootstrap页面
2. 居中的标题和按钮
注意居中：通过文本对齐类，可以简单方便的将文字重新对齐，如class="text-center"
-->
<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Hello World</title>
    <link rel="stylesheet" href="http://netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
</head>
<body>
<div class="text-center">
    <h1>Hello World!</h1>
    <button class="btn btn-primary btn-lg">我是按钮，点我一下！</button>
</div>
<button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="left" title="Tooltip on left">Tooltip on left</button>
<button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="top" title="Tooltip on top">Tooltip on top</button>
<button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="bottom" title="Tooltip on bottom">Tooltip on bottom</button>
<button type="button" class="btn btn-default" data-toggle="tooltip" data-placement="right" title="Tooltip on right">Tooltip on right</button>
<script src="http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js"></script>
<script src="http://cdn.bootcss.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
</body>
</html>